For knife-edge flight with a Seamaster --- go back to post #6. The Seamaster will KE very well with that simple mod. You will not need anything better than standard bb servos (Hitec HS 425, or Futaba 3004) & a good 46 engine with a Tower muffler (TT 46 Pro, OS 46 FX/AX) or an OS 50 SX (perfect).